MODELING THE INTERACTIONS BETWEEN HYDROPHILIC NONIONIC POLYMERS AND CHARGED LIPID VESICLES - A THEORETICAL AND CALORIMETRIC INVESTIGATION OF THE POLY(ETHYLENE GLYCOL) PHOSPHOLIPID SUSPENSIONS

The interaction between charged lipid vesicles suspended in an electrolyte solution containing uncharged polymers has been described by a theoretical model and some of the main predictions have been tested by differential scanning calorimetry (DSC) measurements. The model takes into account neutralization of the lipid head groups through the adsorption of specific ions. The distribution of the ions and polymer and the charge density on the vesicle's surface have been considered as variational parameters which can be calculated by minimizing the total free energy of the system. The model has been used to calculate the effect of the polymer on the lateral peak separation of lipids in the vesicle, and the inhomogeneous lipid distribution has been detected as a splitting of the calorimetric peak associated with the gel to liquid-crystal phase transition.